We propose to use mutants, antimetabolites and nutritional shifts to investigate the mechanism by which nutritional restriction increases the lifespan and slows the aging of the soil nematode Caenorhabditis elegans. First, a variety of complex and defined culture media will be tested, both to determine whether a specific nutrient or the general caloric intake is most critical in determining lifespan and to establish a standard pair of conditions, one enriched and one deprived, which give very different aging rates. Then we will attempt to formulate an operational definition of "aging" in terms of a set of best parameters which show progressive, deteriorative changes with age. Behavioral, physiological, metabolic and biochemical parameters will be screened, and we will require that the chosen test parameters show an invariant order under both standard conditions, despite the aging rate difference. Once the test parameters are identified, we will use them to examine how antimetabolites, nutritional shifts and mutations affect the aging rate. Specifically, we will attempt to block major metabolic groups and thereby produce under enriched conditions the slower aging rate characteristic of deprived conditions. Particular attention will be given to the reactions of energy generation and energy utilization, as these are the most obvious targets of nutritional influence.